On Mon, May 05, 2014 at 10:55:37AM +0200, Ingo Molnar wrote: > > * Josh Poimboeuf <jpoim...@redhat.com> wrote: > > > [...] > > > > kpatch checks the backtraces of all tasks in stop_machine() to > > ensure that no instances of the old function are running when the > > new function is applied. I think the biggest downside of this > > approach is that stop_machine() has to idle all other CPUs during > > the patching process, so it inserts a small amount of latency (a few > > ms on an idle system). > > When live patching the kernel, how about achieving an even 'cleaner' > state for all tasks in the system: to freeze all tasks, as the suspend > and hibernation code (and kexec) does, via freeze_processes()? > > That means no tasks in the system have any real kernel execution > state, and there's also no problem with long-sleeping tasks, as > freeze_processes() is supposed to be fast as well. > > I.e. go for the most conservative live patching state first, and relax > it only once the initial model is upstream and is working robustly.
I had considered doing this before, but the problem I found is that many kernel threads are unfreezable. So we wouldn't be able to check whether its safe to replace any functions in use by those kernel threads. -- Josh -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
